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Littérature scientifique sur le sujet « SILICA SYSTEMS »

Auteur : Grafiati

Publié le 1 avril 2023

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Articles de revues sur le sujet "SILICA SYSTEMS"

Caponi, S., P. Benassi, R. Eramo, A. Giugni, M. Nardone, A. Fontana, M. Sampoli, F. Terki et T. Woignier. « Phonon attenuation in vitreous silica and silica porous systems ». Philosophical Magazine 84, n^o 13-16 (mai 2004) : 1423–31. http://dx.doi.org/10.1080/14786430310001644170.

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Shchukin, D. G., D. V. Sviridov et A. I. Kulak. « Magnetorheological photocatalytic systems ». International Journal of Photoenergy 1, n^o 2 (1999) : 65–67. http://dx.doi.org/10.1155/s1110662x99000124.

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Preparation and properties of a novel photocatalytic system containing magnetic cores coated with subsequently applied silica and titania shells are discussed. The underlying idea is to impart magnetic properties to the semiconductor particles that permits to control the rheological properties of the photocatalyst dispersion and makes possible its separation from treated solution without invoking procedures of filtration or centrifugation. Preparation route yielding photoactive titania coating and silica interlayer, which prevents the undesirable doping of catalyst and parasitic charge exchange between titania shell and magnetic core, is described in detail.

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Caponi, S., A. Fontana, M. Montagna, O. Pilla, F. Rossi, F. Terki et T. Woignier. « Acoustic attenuation in silica porous systems ». Journal of Non-Crystalline Solids 322, n^o 1-3 (juillet 2003) : 29–34. http://dx.doi.org/10.1016/s0022-3093(03)00167-4.

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Carvalho, A., P. J. Sebastião, I. Fonseca, J. Matos et M. Clara Gonçalves. « Silica and silica organically modified nanoparticles : Water dynamics in complex systems ». Microporous and Mesoporous Materials 217 (novembre 2015) : 102–8. http://dx.doi.org/10.1016/j.micromeso.2015.06.015.

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Weng, Peter F. « Silica scale inhibition and colloidal silica dispersion for reverse osmosis systems ». Desalination 103, n^o 1-2 (novembre 1995) : 59–67. http://dx.doi.org/10.1016/0011-9164(95)00087-9.

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Salimian, S., A. Zadhoush et A. Mohammadi. « A review on new mesostructured composite materials : Part I. synthesis of polymer-mesoporous silica nanocomposite ». Journal of Reinforced Plastics and Composites 37, n^o 7 (10 janvier 2018) : 441–59. http://dx.doi.org/10.1177/0731684417752081.

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Mesoporous silicas are inorganic materials with large surface areas, uniform framework structures and readily controlled pore diameters which are synthesized in the presence of surfactants as structure-directing agents, followed by the removal of the surfactant by extraction or calcination. Due to their characteristics, such as ordered structure, high surface area, and favorable interfacial interactions between silica surface and the polymer, they have found excellent potential application for use as reinforcing agents for several engineering polymer systems. While a large number of different synthesis approaches for the preparation of mesoporous silica-polymer nanocomposites has been reported in literature, there is nevertheless a growing need for verified synthesis methods of mesoporous silica-polymer materials. This paper presents a review of the literature on the methods for synthesizing polymer-mesoporous silica nanocomposites and discusses some unique properties of these composites.

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Phoenix, Vernon R., Kurt O. Konhauser et F. Grant Ferris. « Experimental study of iron and silica immobilization by bacteria in mixed Fe-Si systems : implications for microbial silicification in hot springs ». Canadian Journal of Earth Sciences 40, n^o 11 (1 novembre 2003) : 1669–78. http://dx.doi.org/10.1139/e03-044.

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The immobilization of silica and iron by the bacteria Bacillus subtilis was monitored in controlled microcosms to elucidate the role iron may play in aiding bacterial silicification in hot springs. Silica and iron immobilization was monitored as a function of bacterial concentration, iron concentration, and silica concentration (both undersaturated and oversaturated with respect to amorphous silica). Results demonstrate that bacterial cells do immobilize more Fe than bacteria-free systems in solutions with iron concentrations [Formula: see text]50 ppm Fe. However, as iron concentrations increase, the difference between Fe immobilization in bacterial and bacteria-free systems decreases as non-bacterially mediated precipitation processes dominate. Additionally, bacterial systems that had immobilized more Fe compared with bacteria-free systems did not immobilize more silica than bacteria-free systems. By comparing molar ratios of (silica in solution)/(bacterially bound Fe), it is evident that insufficient iron is bound to the bacterial surface to act as an effective salt bridge for silica sorption. This appears to be because much of the iron is immobilized by non-bacterially mediated precipitation of phases such as Fe(OH)3 and poorly ordered hydrous iron silicates. It follows that in silica-enriched hot springs, silica and iron immobilization processes are significantly dominated by non-bacterially mediated precipitation. Any bacterially mediated processes are exceedingly small and outside the resolution of these experiments.

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Komiyama, Masaharu, et Manabu Kirino. « First STM Observation of Silica and Platinum-on-Silica Model Catalyst Systems ». Chemistry Letters 21, n^o 12 (décembre 1992) : 2301–2. http://dx.doi.org/10.1246/cl.1992.2301.

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Godoi, R. H. M., L. Fernandes, M. Jafelicci Jr, R. C. Marques, L. C. Varanda et M. R. Davolos. « Investigation of the systems silica and silica containing chromium in alcohol medium ». Journal of Non-Crystalline Solids 247, n^o 1-3 (juin 1999) : 141–45. http://dx.doi.org/10.1016/s0022-3093(99)00052-6.

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Nowacka, Magdalena, Łukasz Klapiszewski, Małgorzata Norman et Teofil Jesionowski. « Dispersive evaluation and surface chemistry of advanced, multifunctional silica/lignin hybrid biomaterials ». Open Chemistry 11, n^o 11 (1 novembre 2013) : 1860–73. http://dx.doi.org/10.2478/s11532-013-0322-4.

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AbstractAdvanced silica/lignin hybrid biomaterials were obtained using hydrated or fumed silicas (Aerosil®200) and Kraft lignin as precursors, which is a cheap and biodegradable natural polymer. To extend the possible range of applications, the silicas were first modified with N-2-(aminoethyl)-3-aminopropyltrimethoxsysilane, and then with Kraft lignin, which had been oxidized with sodium periodate. The SiO2/lignin hybrids and precursors were characterised by means of determination of their physicochemical and dispersive-morphological properties. The effectiveness of silica binding to lignin was verified by FT-IR spectroscopy. The zeta potential value provides relevant information regarding interactions between colloid particles. Measurement of the zeta potential values enabled an indirect assessment of stability for the studied hybrid systems. Determination of zeta potential and density of surface charge also permitted the quantitative analysis of changes in surface charge, and indirectly confirmed the effectiveness of the proposed method for synthesis of SiO2/lignin hybrid materials. A particularly attractive feature for practical use is their stability, especially electrokinetic stability. It is expected that silica/lignin hybrids will find a wide range of applications (polymer fillers, biosorbents, electrochemical sensors), as they combine the unique properties of silica with the specific structural features of lignin. This makes these hybrids biomaterials advanced and multifunctional.

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Thèses sur le sujet "SILICA SYSTEMS"

Perry, Carole Celia. « Silicification in biological systems ». Thesis, University of Oxford, 1985. http://ora.ox.ac.uk/objects/uuid:ae665ac4-63eb-4963-845a-d2db6aea31a6.

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This thesis is concerned with the formation and structure of silicified deposits in biology. The major system studied is silicified macrohairs from the lemma of the grass Phalaris canariensis L. The macrohairs consist of silica and polysaccharides. Chemical and structural studies on the mineral phase utilised electron microscopy (transmission (TEM), scanning (SEM) and ultra high resolution (HRTEM)), energy disoersive X-ray analysis (EDXA), solid state nuclear magnetic resonance ( ᷣ⁹ Si nmr), infrared spectroscopy, birefringence and nitrogen adsorption experiments. Results showed that the silica is chemically 'pure', hydrated, amorphous at a resolution of 1OÅ and a variety of structural morphologies were observed which are related to the maturity of the macrohair. Analytical studies at different times after emergence of the inflorescence utilising EDXA and scanning proton microprob eanalysis (SPM) showed that the inorganic elements Si, K, P, S and Cl are spatially organised within the macrohairs during silicification. It is proposed that the macrohairs are silicified under strict cellular control. The organic matrix in the mature macrohairs was investigated by acid hydrolysis and chromatography. The changing emphasis of polysaccharide synthesis in the macrohairs as mineralisation occurs was followed by in vivo radioactive labelling of inflorescences at different stages using ⁱ⁴C glucose and Harabinose. Analysis o fpolysaccharides synthesised involved acid hydrolysis and enzymic digestions (Amylase and Driselase), followed by paper and thin layer chromatography with scintillation counting of the products. Results showed that at the early stages of mineralisation, arabinoxylans and cellulose are the major polymers synthesised but as the macrohair matures, largely non-cellulosic glucans (as yet unidentified) are synthesised. It is proposed that the change in emphasis of polysaccharide synthesis during wall development is related to the size and ultrastructural arrangements of silica particles observed. The organic matrix was also observed to give additional order to the system, the resulting material being totally impervious. A second system, chosen for comparison, is mineralised teeth from the radula of the common limpet Patella vulgata. The mature teeth contain silica, iron oxide (goethite) and an organic matrix. Investigations on the silicified phase utilising electron microscopy revealed morphological structural variations. Analytical studies involving EDXA and SPM analysis showed that there are complex temporal and spatial variations in the inorganic composition (P, S, Ca, Fe, Si, Cu) in all regions of the teeth. It is proposed that these changes can be correlated with changes in composition of the organic matrix. A comparison is made of the silica from the two systems.

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Turner, Richard John. « The rheology and structure of aqueous gelatin-silica systems ». Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274624.

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Kokhanenko, Pavlo. « Hydrodynamics and chemistry of silica scale formation in hydrogeothermal systems ». Thesis, University of Canterbury. Mechanical Egineering, 2015. http://hdl.handle.net/10092/10247.

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The extraction of geothermal heat can cause precipitation of the minerals dissolved in geothermal fluid. Their deposition on the walls of wells and above-ground plant and in pores near reinjection wells, also known as mineral scaling, is one of the main obstacles to increasing the effectiveness of utilization of the limited geothermal resources. If not controlled properly it can result in accumulation of a significant amount of scale which obstructs pipes and reinjection wells and reduces the efficacy of heat exchangers. The most abundant mineral in geothermal fluid is silica and thus its precipitation can cause the highest scaling rate. While this dissertation is devoted to the study of silica scaling the results obtained may be applicable to other minerals with similar deposition mechanism. Oversaturated silica is known to precipitate from aqueous solution either by the direct chemisorption of single silicic acid molecules (monomers) or by forming colloidal particles suspended in the solution. These particles can subsequently be transported to, and attach onto, a wall. This process of colloidal silica deposition was previously recognised to cause much faster scaling than the direct deposition of silica monomers under typical geothermal plant conditions. While the chemical kinetics of silica polymerization and colloid formation are relatively well understood, transport of these colloids and their stability, which control their aggregation and attachment rates, on the other hand are not. Previous studies of the silica scaling process have identified prominent effects of geothermal brine hydrodynamics on the scaling rate. It was found to increase with the flow rate and particle size, thus suggesting the dominance of the advective (inertial) deposition of colloidal silica. However, this conclusion contradicted the present theory of particle transport in turbulent flows which argues the dominance of the diffusive transport for the relevant range of particle sizes (<1 μm). The development and continuing improvement of the anti-scaling measures required deeper understanding of the complex combination of the phenomena involved in the process of silica scaling. This was pursued in the present study using theoretical and experimental methods. First, the rate of colloidal silica transport from a turbulent flow onto the internal surface of a circular pipe, a cylinder and a flat plate were calculated using available analytical and numerical methods. The obtained theoretical transport rate was found to be about four orders of magnitude higher than the corresponding experimental scaling rate. The latter was determined in the previous studies to be 4.2·10-8 kg/s/m2 for silica colloids of 125 nm in diameter which corresponded to the dimensionless deposition velocity (the dimensionless deposition velocity is the scaling rate normalised by the particle mass concentration and friction velocity) of 1.2·10-6 for the dimensionless particle relaxation time of 2·10-4. Next, based on the standard DLVO theory of particle interactions and in the framework of the Smoluchowski approach the probability of colloidal silica particle attachment to a wall was found to be 10-6. Therefore, the theoretical scaling rate, calculated as a product of this probability and the above-mentioned transport rate was two orders of magnitude lower than the experimental scaling rate. This suggested that the implemented theoretical approach either underestimated particle transport rate or overestimated particle stability. Both possibilities are explored in this dissertation. In addition, the silica scaling rate was measured for a range of conditions: particle size from 20 to 60 nm, particle concentration 1600-10000 ppm, friction velocity from 0.09 to 0.18 m/s (Re = 9-50·103) and ionic strength from 30 to 80 mM, pH 8.1-9.5 and temperature from 25 to 44 °C. For this, laboratory experiments were designed and progressively modified in order to improve the repeatability of the results and to study the scaling process. In these experiments colloidal silica deposition onto the walls of mild steel pipe sections was studied with a recirculating flow rig with variable (but controllable) particle size, concentration, flow rate, pH and ionic strength of the solution. In addition, a parallel plate flow test section was designed and built which will provide better capabilities for the control over the hydrodynamic and test surface conditions in future experiments. The control over the chemical conditions was achieved by the use of the synthetic colloidal solutions. Two methods of their production – hydrolysis of either sodium metasilicate or active silicic acid – were employed. The influence of the synthesis conditions, ion content and pH on the long term behaviour of these colloidal solutions was investigated. The particle size data, obtained using dynamic light scattering (DLS) and verified by electron microscopy, was analysed and compared against the predictions of the current models of nanoparticle growth and stability. The kinetic aggregation was identified to be the dominant particle growth mechanism. Experimental data collected during the long-term observations of the particle growth allowed relationships between the aggregative stability and such parameters as the particle size, ion concentration and pH of the solution to be elucidated. In particular, the aggregative stability of 10-20 nm particles was found to be 108-1010 which is 7-9 orders of magnitude higher than the corresponding DLVO stability. It was also found to decrease with the increase of the particle size. This agreed with the theory of the colloid stabilization by steric interactions. Moreover, the model of the “gel” layer was used to explain the observed “anomalies” of the colloidal silica behaviour. The deposition experiments conducted with these synthetic colloidal solutions showed that the scaling rate increased with the particle size, flow rate and ionic strength (IS) of the solution. Thus, it was measured to be 9.7·10-9 kg/s/m2 for the 45 nm particles in a solution with IS = 0.05 M, which corresponded to the dimensionless deposition velocity of 6.6·10-8 for a dimensionless particle relaxation time of 2.2·10-6. The scaling rate was calculated for these conditions by multiplying the corresponding transport rate and the actual attachment probability determined as an inverse of the experimental stability. It was found to agree with the experimental value within an order of magnitude. In addition, the observed increase of the scaling rate with the increase of particle size was explained by the compensation of the decreased rate of the particle transport by faster decrease of actual particle stability (increase in attachment probability). Therefore the contradiction between the theory and the experiment was resolved for the particles of 20 to 60 nm in diameter. Moreover, the observations of the dimensions and distribution of the scale elements formed in some of the present experiments strongly suggested the significance of the advective (inertial) mechanism of particle deposition. This and comparative analysis of other experimental and theoretical data suggested that the present theory may underestimate the convective transport of the particles onto a rough wall. Therefore, the hypothesis of the parallel-to-wall advective deposition of the nanoparticles onto the roughness/scale elements (not accounted in the current theory) was proposed. The corresponding mass transfer problem was solved analytically using experimentally found dimensions of the scale elements. The additional transport was found to decrease the above-stated discrepancy between the theoretical and experimental scaling rate for large (125 nm) particles by one order of magnitude. The remaining difference of one order of magnitude was speculated to be due to the underestimation of these particles attachment probability derived with the standard DLVO theory. The actual aggregative stability of the silica colloids larger than 60 nm in diameter and for a wider range of IS values is of interest for future experimental studies. An improved understanding of the interrelation between the chemical and hydrodynamic phenomena in the process of silica scaling and its dominant mechanisms was achieved in this dissertation. This allowed optimization of the present anti-scaling practices aimed to minimize the negative effects of mineral scaling on the operation of geothermal power stations. Besides the practical recommendations, which may ultimately help to increase the efficiency of geothermal power stations, the results of the present study may be of value in the fields of mass transfer and colloid science.

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Rashchi, Fereshteh. « Adsorption on silica in Pb- and Ca-SO4-CO3 systems ». Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27252.

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Formation of Pb and Ca precipitates on a silica surface in the presence of sulphate and carbonate under neutral to alkaline condition is studied using zeta potential measurements, Scanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS). The effect of carbonate on displacing sulphate is discussed.
In the Pb/sulphate system, precipitates of predominantly Pb-oxide/hydroxide formed on the silica surface. In the Pb/carbonate system, the precipitates were predominantly Pb-carbonate/hydroxy carbonate. Precipitates in both the Pb/SO$ sb4$ and Pb/CO$ sb3$ systems were dispersed by addition of sufficient carbonate, the silica surface eventually becoming free of precipitates. This dispersion was considered to be due to: a high negative surface charge density on both lead carbonate and silica; nucleation being promoted at high concentrations of carbonate, resulting in small precipitates; and increased solubility at high carbonate concentrations.
In the Ca system, calcium sulphate precipitates did not form on the silica particles while calcium carbonate precipitates did. The precipitates were not removed by increasing carbonate concentration. The difference from the Pb system is attributed to a low negative surface charge density on calcium carbonate compared to lead carbonate, leading to less dispersing conditions, and the higher solubility of calcium sulphate compared to lead sulphate.

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Meadows, Philippa Jill. « Template-directed synthesis of silica materials based on self-assembling systems ». Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439957.

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Rezk, Ahmed Rezk Masoud. « Theoretical and experimental investigation of silica gel/water adsorption refrigeration systems ». Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3623/.

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This PhD project was set out to improve the performance of silica gel / water adsorption cooling systems using a number of investigation tools. A novel global lumped analytical simulation model has been constructed for a commercialised two-bed silica gel / water 450kW adsorption chiller. It was integrated with a genetic algorithm (GA) optimisation toolbox to determine the optimum operating conditions to obtain the optimum chiller performance. The model was used to investigate the effect of physical and operating on the chiller performance. The model was also used to investigate the effect of various adsorbent bed enhancement techniques that are presented in published literature. An experimental test facility has been designed, constructed and commissioned to study the performance of scaled down adsorbent bed modules. It has been constructed to understand the effect of the operating conditions on adsorbent-bed heat and mass transfer performance. A dynamic vapour sorption (DVS) gravimetric analyser has been used to characterise a new species of adsorbents (MOFs). These adsorbents have strong potential towards water sorption and could replace the currently applied silica gel. MOFs adsorbents have been characterised in terms of adsorption isotherms and kinetics, in addition to its cyclic analysis. It was found that HKUST-1 (copper based MOF) outperforms silica gel with 95.7% increase in the water uptake. Iron based MOF (MIL-100) was found to outperform silica gel for high evaporating temperature application.

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Neugebauer, Adam (Adam Halbert). « Thermal properties of granular silica aerogel for high-performance insulation systems ». Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85213.

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Thesis: S.M. in Building Technology, Massachusetts Institute of Technology, Department of Architecture, 2013.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 65-67).
Based on mounting evidence in support of anthropogenic global climate change, there is an urgency for developments in high-performance building techniques and technologies. New construction projects provide substantial opportunities for energy efficiency measures, but they represent only a small portion of the building stock. Conversely, while existing buildings are plentiful, they typically have a much narrower range of feasible energy efficiency options. Therefore, there will continue to be a need for the development of new and improved energy efficiency measures for new building construction and even more so for deep retrofits of existing buildings. This thesis provides an overview of the research performed into the on-going development at MIT of a high-performance panelized insulation system based on silica aerogel. Two test methods were used for measuring the thermal conductivity of the granules: the transient hot-wire technique and the guarded hot-plate system. Utilizing the hot-wire set-up, it was demonstrated that compressing a bed of granules will decrease the thermal conductivity of the system until a minimum point is reached around the monolithic density of the aerogel. For the Cabot granules, this was seen at 13 mW/m-K and about 150 kg/m3. The MIT granules showed equal performance to the Cabot granules at bed densities 20-30 kg/m3 lower. The hot-plate testing was able to experimentally evaluate previous analytical predictions regarding the conductivity impact of the internal panel truss and the under-prediction of radiant heat transfer in the hot-wire method. Hot-wire testing was also done in a vacuum chamber to quantify potential performance improvements at reduced air pressures. Since a vacuum would require the incorporation of a barrier film into the panel system, some analyses were done into the thermal bridging potential and gas diffusion requirements of such a film. Additionally, physical prototyping was done to explore how the film would be incorporated into the existing panel design. The aerogel-based insulation panel being developed at MIT continues to show promise, though there are still plenty of opportunities remaining in the development cycle.
by Adam Neugebauer.
S.M. in Building Technology

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Huang, Pengyu. « Multiscale Modelling of Dynamic Contact Angles for CO2-Water-Silica Systems ». Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20937.

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The capillary and dynamic wetting behaviour in porous media is crucial in many engineering problems which are highly related to the multiphase interactions between fluids and solids. This thesis will focus on the behaviour of dynamic contact angle of the supercritical CO2/water flow in the silica slit as a function of the contact line velocity at both the nanoscale and microscale, which can help us gain an in-depth understanding of the dynamic processes in CO2 geosequestration in saline aquifers. Our molecular dynamics (MD) simulations calculate the contact angle quantitatively at different velocities at the nanoscale and also validate the molecular kinetic theory through the detailed analysis of the equilibrium jump distance and frequency of the water and CO2 molecules at the solid surfaces. While the MD simulations provide the results of dynamic contact angle at the nanoscale, which can be suitable for the nanopores of the low permeability rock, the dynamic contact angle behaviour at the microscale is also important and investigated in this thesis. This work also develops a coarse-grained molecular dynamic (CGMD) framework to model the liquid-vapour-solid interactions at the microscale. The newly developed CGMD framework has been applied and extended to the study of the dynamic contact angle for the CO2-water-silica system at the microscale. The microscale CGMD simulation of CO2-water-silica system shows that there is an increase in the CO2 contact angle as the increase of the contact line velocity at three different pressures. The dynamic contact angles under a water pressure of 18.9 MPa seem to be slightly larger than those under the water pressures of 9.41 MPa and 14.3 MPa. Moreover, the comparison between the MD and CGMD results suggests that there could be a pore size effect on the dynamic contact angle for the studied CO2-water-silica system.

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NAIRI, VALENTINA. « Functional ordered mesoporous silica in nanomedicine : target and drug delivery systems ». Doctoral thesis, Università degli Studi di Cagliari, 2018. http://hdl.handle.net/11584/255981.

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Ordered mesoporous materials (OMMs) are characterized by high surface area (up to 1000 m2/g), high pore volume (1-3 cm3/g) and narrow pore size (2-30 nm) distribution. Recently, mesoporous silica nanoparticles (MSNs), a subclass of OMMs, have had great development as nanocarriers for drug delivery, particularly for cancer treatment. The research activity of my PhD work was aimed to study SBA-15 and MCM-41 mesoporous silica samples for biomedical applications. The texture and the structure of the synthesized materials were characterized through N2 adsorption/desorption isotherms, SAXS, and TEM. The functionalization of the mesoporous silica samples was verified by means of Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). DLS and ELS were used to determinate hydrodynamic diameter and zeta potential of the studied systems under different conditions. The PhD thesis focused on different aspects of the use of OMMs, particularly MSNs, as drug nanocarriers. In the first paper how different features of OMMs (surface area, pore size and surface charge) can affect the adsorption and release of drugs was investigated. Ampicillin, a penicillin-like -lactam antibiotic was loaded on MCM-41, SBA-15, and amino-functionalized SBA-15, then its release in simulated physiological conditions was studied. This study demonstrated that to obtain a sustained drug release, the chemical nature of the matrix’s surface plays a role which is more important than its textural features. SBA-15-NH2 matrix is a suitable candidate as depot system for local sustained release of ampicillin. Common target systems have the disadvantage that the targeting molecule can be recognized by several receptors. A possible strategy to solve this issue was investigated in the second paper. The targeting molecule was hidden by preparing a double sequential targeting system. To this purpose a double target system was synthesized. Alendronate was used as a tissue target to recognize a diseased bone, and an encrypted cellular target, Arg-Gly-Asp (RGD) was used to improve the internalization in human osteosarcoma cells (collaboration with Universidad Complutense de Madrid). This preliminary study showed the efficacy of the double target systems. The next step could be the functionalization of MSNs with the previously described systems for the synthesis of a smart target systems usable as a carrier for anticancer drugs against bone cancer. In the third paper, the effect of surface charge on the internalization of MCM-41-type MSNs, functionalized with chitosan (CHIT) and hyaluronic acid (HA) biopolymers, on 3T3 mouse fibroblast cells was then investigated. The opposite surface charge of the biopolymer-functionalized MSNs (negative for MSN-HA and positive for MSN-CHIT) gave a different interaction with BSA, used as a model protein to investigate the formation of the protein corona (forth paper). Finally, in the fifth paper, MSNs were functionalized with HA samples having three different molecular weights (HAS, HAM, and HAL). The effect of HA molecular weight on the internalization of HA-MSNs particles on HeLa cells was evaluated. These last studies showed the importance of the external functionalization on the interaction between MSNs and the components of body fluids, that change their surface properties. These changes as well as the polymer’s features (i.e. the molecular weight) are able to modulate the cellular uptake. The obtained results highlight the importance of the physico-chemical phenomena occurring at the nano-biointerface for the future use of functionalized OMMs and MSNs in nanomedicine. The present findings confirm that these nanocarriers are very promising matrices for the obtainment of targeting drug delivery systems for cancer treatment.

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Rahman, Shaily. « Cosmogenic Silicon-32 reveals extensive authigenic clay formation in deltaic systems and constrains the marine silica budget ». Thesis, State University of New York at Stony Brook, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10140185.

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Cosmogenic ³²Si (t_1/2 ∼ 140 yrs) was used in a novel way to constrain the quantity of reactive Si storage and early diagenetic reactions of Si in the highly mobile deltaic sediments along the coast of French Guiana, representative of deposits along the ~1600 km Amazon–Guianas coastline downdrift of the Amazon delta. A sequential leach was developed to extract and purify SiO₂ from different operational pools in large samples of surface sediments (0–10cm). This methodology, a hot 1% Na₂CO₃ leach followed by a hot 4M NaOH leach, was adapted from the existing leaches widely used to estimate biogenic silica (bSi) content in marine sediments, and ultimately to constrain the global oceanic Si budget. ³²Si activity was determined in each pool via its daughter product ³²P. Results from several sites in coastal mudbanks near Kourou and Sinnamary indicate no detectable ³²Si activity in the bSi fraction, whereas ³²Si was detected in the Si-NaOH fraction after removal of bSi. The lack of detectable activity in the 1% Na₂CO₃ leach and its detection in the NaOH fraction (0.4–2.5 dpm) indicate that the method widely used to determine bSi content recovers only a minor fraction of the originally deposited reactive bSi in these deposits. The results are consistent with rapid alteration of biogenic silica and clay authigenesis or reverse weathering. They also demonstrate that the current estimate of biogenic silica storage in tropical deltaic sediments is significantly underestimated. Assuming an initial diatom specific activity range of ∼5–40 dpm/kg SiO₂, the ³²Si activity in the NaOH fraction corresponds to a reactive Si storage of ∼150–18,000 µmol Si/g sediment. This magnitude is more consistent with estimates of reactive Si (ΣSi_hr) storage in the Amazon delta based on modified operational leach techniques that target poorly crystalline clays and with diagenetic modeling of pore water K⁺, F⁻, and Si(OH)₄, though these modified leaches also appear to underestimate the amount of reactive Si stored along this system. To directly confirm whether these modified operational extractions underestimate reactive Si storage, a sequential extraction methodology was also developed to first isolate ³²Si activity in the ΣSi_hr fraction (0.1N HCl followed by 1% Na₂CO₃) and then extract any remaining ³²Si from the residual fraction using 4M NaOH.

Sediment from 2 stations in the Gulf of Papua, Papua New Guinea, 1 station in the northern Gulf of Mexico near the Southwest Pass, and 1 station in Long Island Sound (Smithtown Bay) were also extracted for ³²Si in the bSi fraction as well as the residual fraction after removal of bSi. Bulk ³²Si activities in the residual fractions in the Gulf of Papua (0.5–0.7 dpm/kg sediment) were used to extrapolate Si storage in the outer topset and forset of the clinoform delta.

³²Si activity was detected in the both the bSi (0.21 ± 0.04 dpm/kg sediment) and the residual fraction (0.44 ± 0.08 dpm/kg sediment) from the site in the Gulf of Mexico. A Si burial rate using the ³²Si activity in the bSi fraction (assuming an activity of 15dpm/kg in starting Si materials) of 0.004Tmol/y was calculated over approximately 5000 km2 of the delta, whereas the burial rate calculated using the Si content in this same fraction from a classic bSi leach, was ∼0.006Tmol/y. Adding the Si burial rate using the ³²Si activity in the residual fraction (0.008Tmol/y) yielded a total storage per year of 0.012Tmol Si, ∼10% of the total Si inputs (dissolved and amorphous Si) from the Mississippi-Atchafalaya river system. ³²Si activity was also detected in the residual fraction (0.53 ± 0.08 dpm/kg sediment) after removal of ΣSi_hr and using this activity yielded similar calculated rates of Si burial (∼0.01 Tmol/y).

In Smithtown Bay, Long Island Sound, ³²Si activity was also detected in both the bSi (0.15 ± 0.05 dpm/kg sediment) and the residual (0.4 ± 0.2 dpm/kg sediment) fractions from the site in Smithtown Bay, Long Island Sound, yielding a total Si storage estimate (assuming an activity of 15 dpm/kg in starting Si materials) of 1.6 × 10⁻³ Tmol/y over the entire Sound, comparable to estimates of Si storage calculated using the Si content in the classic bSi (1.1 × 10⁻³ Tmol/y) and the classic ΣSi_hr (2.2 × 10⁻³ Tmol/y) leaches. It appears that reverse weathering is an important sink of Si in these deposits and that classic bSi or ΣSi_hr leaches can underestimate Si storage in these system by two to four-fold. (Abstract shortened by UMI.)

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F, Digonnet Michel J., et Society of Photo-optical Instrumentation Engineers., dir. Doped fiber devices and systems : 25-26 July 1994, San Diego, California. Bellingham, Wash., USA : SPIE, 1994.

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United States. National Aeronautics and Space Administration., dir. Final report on the development of methodologies and solvent systems to replace CFC-113 in the validation of large-scale spacecraft hardware : NASA research grant award no. NAG10-0169. [Washington, DC : National Aeronautics and Space Administration, 1996.

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United States. National Aeronautics and Space Administration., dir. High speed, precision motion strategies for lightweight structures. [Washington, DC : National Aeronautics and Space Administration, 1987.

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United States. National Aeronautics and Space Administration., dir. High speed, precision motion strategies for lightweight structures : Semiannual progress report, May 15, 1988 to November 14, 1988. [Washington, DC : National Aeronautics and Space Administration, 1989.

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Guo, Wei, Min Qian, Xiaoyi Zhang et Yi Wang. « Silica-Based Tumor-targeted Systems ». Dans New Nanomaterials and Techniques for Tumor-targeted Systems, 271–92. Singapore : Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5159-8_8.

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Choudhari, Yogesh, Hans Hoefer, Cristian Libanati, Fred Monsuur et William McCarthy. « Mesoporous Silica Drug Delivery Systems ». Dans Advances in Delivery Science and Technology, 665–93. New York, NY : Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-1598-9_23.

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Schuck, G., W. Dietrich et J. Fricke. « Pore Size Distribution of Silica Systems ». Dans Springer Proceedings in Physics, 148–53. Berlin, Heidelberg : Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-93313-4_19.

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Dubin, Leonard. « Silica Inhibition in Cooling Water Systems ». Dans ACS Symposium Series, 354–79. Washington, DC : American Chemical Society, 1991. http://dx.doi.org/10.1021/bk-1991-0444.ch025.

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Ishizuka, Norio, Hiroyoshi Minakuchi, Kazuki Nakanishi, Masanori Motokawa, Kouji Takahashi, Masahiro Furuno et Nobuo Tanaka. « Monolithic Silica Columns for Capillary HPLC ». Dans Micro Total Analysis Systems 2002, 602–4. Dordrecht : Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0295-0_201.

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Ishizuka, Norio, Hiroyoshi Minakuchi, Kazuki Nakanishi, Kazuyuki Hirao, Masanori Motokawa, Hiroshi Kobayashi et Nobuo Tanaka. « Monolithic Silica Columns for Micro-HPLC ». Dans Micro Total Analysis Systems 2001, 555–56. Dordrecht : Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-1015-3_240.

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Gupta, Alok Krishna. « Ternary Systems with Feldspathoids ». Dans Origin of Potassium-rich Silica-deficient Igneous Rocks, 259–76. New Delhi : Springer India, 2015. http://dx.doi.org/10.1007/978-81-322-2083-1_7.

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Gupta, Alok Krishna. « Melilite- and Leucite-Bearing Systems ». Dans Origin of Potassium-rich Silica-deficient Igneous Rocks, 311–36. New Delhi : Springer India, 2015. http://dx.doi.org/10.1007/978-81-322-2083-1_10.

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Gupta, Alok Krishna. « Leucite- and Feldspar-Bearing Systems ». Dans Origin of Potassium-rich Silica-deficient Igneous Rocks, 289–309. New Delhi : Springer India, 2015. http://dx.doi.org/10.1007/978-81-322-2083-1_9.

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Drake, J. M., P. Levitz et J. Klafter. « In Search of Scaling Laws in Porous Silica Gels ». Dans Large-Scale Molecular Systems, 275–81. Boston, MA : Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-5940-1_16.

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Actes de conférences sur le sujet "SILICA SYSTEMS"

Borrelli, N. F., C. Smith et D. C. Allan. « "Laser-Induced Densification in Silica and Binary Silica Systems" ». Dans Wavelength Division Multiplexing Components. Washington, D.C. : OSA, 1999. http://dx.doi.org/10.1364/wdm.1999.267.

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Borrelli, N. F., C. Smith et D. C. Allan. « “Laser-Induced Densification in Silica and Binary Silica Systems” ». Dans Bragg Gratings, Photosensitivity, and Poling in Glass Waveguides. Washington, D.C. : OSA, 1999. http://dx.doi.org/10.1364/bgpp.1999.ca1.

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Ikushima, Akira J., Hiroshi Kakiuchida et Kazuya Saito. « Silica glass for photonics ». Dans Optoelectronic Information Systems and Processing, sous la direction de Yuri N. Kulchin et Oleg B. Vitrik. SPIE, 2001. http://dx.doi.org/10.1117/12.435878.

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Ikushima, Akira J. « Structural Relaxations in Silica Glass ». Dans SLOW DYNAMICS IN COMPLEX SYSTEMS : 3rd International Symposium on Slow Dynamics in Complex Systems. AIP, 2004. http://dx.doi.org/10.1063/1.1764226.

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Petrisor, Gabriela, Ludmila Motelica, Roxana Trusca, Vladimir Lucian Ene, Denisa Ficai, Ovidiu Cristian Oprea, Georgeta Voicu et Anton Ficai. « Mesoporous Silica Systems Loaded with Polyphenols ». Dans Priochem 2021. Basel Switzerland : MDPI, 2022. http://dx.doi.org/10.3390/chemproc2022007015.

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Natoli, Jean-Yves, Bertrand Bertussi, Laurent Gallais, Mireille Commandre et Claude Amra. « Multiple pulses laser irradiation study in silica ». Dans Optical Systems Design, sous la direction de Claude Amra, Norbert Kaiser et H. Angus Macleod. SPIE, 2004. http://dx.doi.org/10.1117/12.513377.

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Cao, Zongliang, Brian VanDerElzen, Kevin J. Owen, Jialiang Yan, Guohong He, Rebecca L. Peterson, Dennis Grimard et Khalil Najafi. « Drie of fused silica ». Dans 2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS). IEEE, 2013. http://dx.doi.org/10.1109/memsys.2013.6474253.

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Vannoni, Maurizio, Andrea Sordini et Giuseppe Molesini. « Fused silica long-term stability : case studies ». Dans SPIE Optical Systems Design, sous la direction de Angela Duparré et Roland Geyl. SPIE, 2011. http://dx.doi.org/10.1117/12.896758.

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Tescione, F., F. Lionetto, C. Esposito Corcione, G. G. Buonocore, R. Striani, M. Lavorgna et M. Frigione. « Morphological characterization of silica obtained by calcination of methacrylic and epoxy – silica hybrid systems ». Dans VIII INTERNATIONAL CONFERENCE ON “TIMES OF POLYMERS AND COMPOSITES” : From Aerospace to Nanotechnology. Author(s), 2016. http://dx.doi.org/10.1063/1.4949635.

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Cormont, Philippe, Stéphanie Palmier, Bertrand Bertussi, Roger Courchinoux, Gael Gaborit, Laurent Gallais, Laurent Lamaignère, Philippe Legros, Jean-Luc Rullier et Hervé Bercegol. « Characterizations of UV-laser damage on fused silica surfaces ». Dans Optical Systems Design, sous la direction de Angela Duparré et Roland Geyl. SPIE, 2008. http://dx.doi.org/10.1117/12.797407.

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Rapports d'organisations sur le sujet "SILICA SYSTEMS"

Popova, Teodora, Borislav Tzankov, Christina Voycheva, Krassimira Yoncheva et Nikolai Lambov. Development of Advanced Drug Delivery Systems with Bicalutamide Based on Mesoporous Silica Particles. "Prof. Marin Drinov" Publishing House of Bulgarian Academy of Sciences, décembre 2019. http://dx.doi.org/10.7546/crabs.2019.12.08.

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Ghassemi, Ahmad. Fracture Propagation and Permeability Change under Poro-thermoelastic Loads & ; Silica Reactivity in Enhanced Geothermal Systems. Office of Scientific and Technical Information (OSTI), octobre 2009. http://dx.doi.org/10.2172/1021468.

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Squires, B. D0 Silicon Upgrad : D0 Silicon Cooling System. Office of Scientific and Technical Information (OSTI), juillet 1998. http://dx.doi.org/10.2172/1032104.

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Cease, Herman. D0 Silicon Upgrade : D-Zero Silicon Cooling System Description. Office of Scientific and Technical Information (OSTI), février 2001. http://dx.doi.org/10.2172/1481379.

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Clarke, Carl L. System Requirements for the Implementation of a Fused Silica Debris Shield. Office of Scientific and Technical Information (OSTI), janvier 2019. http://dx.doi.org/10.2172/1499968.

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Zhu, Jinying, Hongbin Sun, Clayton Malone, Paul Ziehl, Li Ai, Mahmoud Bayat, Ying Zhang, Taeyong Shin et Eric Giannini. Online Monitoring System for Concrete Structures Affected by Alkali-Silica Reaction. Office of Scientific and Technical Information (OSTI), décembre 2021. http://dx.doi.org/10.2172/1838356.

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Markley, Dan. D-Zero Silicon Cooling System Moisture Injection System Control System. Office of Scientific and Technical Information (OSTI), septembre 2009. http://dx.doi.org/10.2172/1462251.

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Cease, Herman. D0 Silicon Upgrade : Engineering Calculation for the Silicon Cooling System. Office of Scientific and Technical Information (OSTI), février 2001. http://dx.doi.org/10.2172/1481391.

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Johnson, R. The GLAST Silicon-Strip Tracking System. Office of Scientific and Technical Information (OSTI), septembre 2004. http://dx.doi.org/10.2172/833101.

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Markley, Dan. D0 Silicon Upgrade : D-Zero silicon Cooling System Monitoring, Interlocks, & ; Alarms. Office of Scientific and Technical Information (OSTI), novembre 2001. http://dx.doi.org/10.2172/1481390.

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